Expulsion gap



INVENTOR.

R. D. NELSON EXPULSION GAP April l1, 1950 Original Filed Sept. 8, 1941Patented Apr. ll, 1950- 2,503,965 axPULsIoN Gar Rolland D. Nelson, HalesCorners, Wis., assignor to McGraw Electric Company, a corporation ofDelaware Original application September 8, 1941, Serial No. 409,925.Divided and this application March 21, 1945, Serial N0. 583,995

z claims. 1

This invention relates to protective apparatus4 for electrical equipmentand transmission lines and has especially to do with lightning arrestersof a variety designated expulsion gaps."

This application is a division of my application for Letters Patentcovering Expulsion device, Serial Number 409,925, illed September 8,1941, now abandoned.

Generally, an expulsion gap comprises a pair of electrodes, one of whichis connected to the line and the other of which is connected to ground;and a spark gap between the electrodes, the gaps being partiallyenclosed by a ber tube carried by one of the electrodes. When lightningor any other electrical surge disturbs the line, the gap is sparked overto relieve the line of its electrical stress.

The arc established between the electrodes causes a fault to betemporarily established between the power line and the ground at thegap, and SCI-cycle, short circuit current begins to flow through the gapchamber. The heat of this arc in combination with moisture driven out ofthe iiber lining of the tube generates a high pressure within the berenclosure. This pressure is relieved through the open end of the tubeand blows the arc out, thereby removing the fault. The expulsion actionlasts until the (S-cycle current Wave passes through zero. At this pointthe fault is eliminated and the line is restored to normal operativecondition.

One object of this invention is to provide an expulsion device whereinthe electrodes remain in xed position relative to each other at alltimes, regardless of .any damage to the tube, thereby always providing asafety valve on the line and giving full protection to the electricalequipment on the line.

Another object is to provide an expulsion device having a mounting meansadaptedto removably receive the expulsion tube and one of the electrodesin fixed, independent relationship to the other of the electrodes.

More speciilcally, it is an object to provide an expulsion devicecomprising a hook and eye type mount, an expulsion tube and electrodeassembly removably carried by the hook and eye mount and a secondelectrode disposed in spaced relationship to the rst electrode and outof axial alignment with the assembly, thereby permitting insertion orremoval of the assembly by an operator by means of a hot-line operatingstick.

A still further object is to provide an expulsion device havingelectrodes positioned relative to each other in such a. manner thatshorting of the line between these electrodes by birds is reduced to aminimum.

Further, an object is to provide an expulsion device having mountingmeans adapted to receive an expulsion tube in xed gap forming positionand which tube may be quickly removed from mounted position by strikingthe tube from one side thereof with any suitable object.

In the drawings:

Fig. i is an elevational view, partly in section, showing the improvedexpulsion device.

Fig. 2 is a view taken on the line 2-2 of Fig. 1.

Fig. 3 is a view taken on the line 3-3 of Fig. l.

My expulsion device comprises an insulating support I provided at itsupper and lower ends with terminal members 2 and 3, respectively,secured in place by means of the bolts l.

A resilient conductor arm 5 is secured to the upper terminal 2 by meansof the bolt 4. The outer end of the conductor arm 5 is provided with aslot 6. A resilient, wire-like holding arm 1 is secured to the terminal2 by means of the bolt I and extends above the conductor arm 5 andterminates in a hooked portion 8 adapted to receive the expulsion tube9.

The expulsion tube 9 comprises an inner ber tube III and an outer tubeII composed of insulating material such as phenolic resin. The upper endof the expulsion tube 9 is provided with a, metal cap I2 secured to thetubes IU and Il by means of a screw I3 which extends into the bore ofthe inner tube I0, operating to hold the electrode Il in position, asshown in Fig. 2. The upper end of the electrode I4 extends out throughan opening I5 provided in the cap I2 and terminates in an eye member I6adapted to be received on the hooked portion 8.

The lower electrode II is secured to the lower terminal member 3 bymeans of bolt 4 and is disposed at the lower end of expulsion tube 9 toone side thereof, out of axial alignment therewith.

The expulsion tube 9 is mounted in posit'on by inserting the lower endof the tube in the gripping head of a specially constructed hot-linestick. The eye member I5 of the electrode I4 is then positioned on thehook portion 8. The tube 9 is then moved in a clockwise directionrelative to Fig. l about the hook 8 in a plane including the members I,5, and Il until the outer end of the conductor arm 5 rides over theupper end of the cap I2 and the upper end of the electrode Il moves intothe slot 6. It is to be noted that the outer end of the conductor arm 5is curved arcuately upwardly at I8 to permit the tube 9 to ride intoposition and bias the members 5 and 1 relative to each other.

An electrical discharge path is established through this device, throughthe terminal 2, the

3 member 1, the electrode Il, the expulsion chamber l9,lthe air gap 20,the electrode I1, and the lower terminal 3.

The terminals 2 and l may be slotted (not shown) to make possible theuse o1' biiurcated connectors (not shown) therewith to eiect lineconnections for the expulsion device.

The expulsion tube 9 may be easily removed from mounted position bystriking the side of the tube 9 near the insulator support l with anysuitable means, thereby quickly and easily disengaging the eye member IIfrom the hook portion 8.

When pressures are built up within the expulsion chamber I9. suiilcientto burst the tube members I and Il. the total gap distance between theelectrodes Il and l1 is not disturbed and the system is left protected.The only difference in the expulsion device under these conditions isthat the expulsion chamber i9 has been destroyed and the air gap 20 hasbeen lengthened to extend between the electrodes I4 and I1.

In the event the expulsion action of the device has been destroyed, theelectrodes I4 and l1 together with the extended air gap 20 provide asafety valve for the system. This safety valve operates in the manner ofan ordinary spark gap without the expulsive characteristics. When theextended air gap is iiashed over, the arc is extinguished when thecircuit is interrupted by the blowing of the line fuse. After this thedamaged expulsion tube is replaced by a new tube and electrode assemblyby means oi a specially constructed hot-line operating stick.

From the foregoing description it is apparent that the objects of thisinvention have been accomplished by providing an expulsion device havingan expulsion tube and electrode assembly adapted to be easily andquickly mounted in operating position; having 'mounting means adapted tomaintain the electrodes in xed position relative to each other under allconditions of operation and to provide means for rapid and easyinstallation of the tube and electrode assembly in operating position.

, tus, the combination with an insulating support including anelectrically conductive arm secured thereto at one end and having itsother end slotted, of a resilient conductive arm secured at one end tothe first mentioned arm and having its other end hook-shaped anddisposed adjacent said slot in spaced relation thereto, the plane of thehook being normal to the plane of said slot, an expulsion tube having aconductive cap at one end contacting a side of the first mentioned armopposite that upon which said resilient arm is disposed, an electricallyconductive rod extending through said cap and into said tube, said rodhaving a portion in said slot and including an eye engaging saidhook-shaped end, and

y means securing said rod in said tube, said resil- UNITED STATESPATENTS Number Name Date 1,946,815 Skipper Feb. 13, 1934 1,958,496 RahMay 15, 1934 2,049,552 Walsh Aug. 4, 1936 2,203,439 Fox June 4, 1940

